In the widely used keg tapping systems of the general type to which this invention relates, each keg is fitted with a keg unit that is seated in its bung hole and comprises a normally closed valve having a plunger-like valve element. The upper portion of the keg unit body is formed with an upwardly opening well, and the body of the tavern unit has a base portion which is so formed as to be rotatably receivable in the well in the keg unit and to provide a bayonet connection with the keg unit. Rotation of the tavern unit to establish and disengage the bayonet connection is facilitated by a lever that projects generally radially from the body of the tavern unit.
Normally, a pressure gas duct and a beverage duct are connected to the tavern unit, and they remain connected to it as the tavern unit is taken off of an empty keg and connected to a full one. The gas duct extends to the tavern unit from a tank charged with pressurized gas, usually carbon dioxide. The beverage duct extends from the tavern unit to a tap at which the beverage is dispensed. When the tavern unit is not connected to a keg unit, a plunger-like valve element in the tavern unit body is normally in a raised position in which it closes the gas duct to prevent loss of pressure gas, while a check valve in that body prevents loss of beverage from the beverage line.
The lever on the tavern unit, which is swingable up and down relative to the body of that unit, serves as an actuator for its plunger-like valve element. When the lever is in a raised position the gas valve is closed. After the bayonet connection between the tavern unit and a keg unit has been fully engaged, the lever is swung down to depress the plunger-like valve element in the tavern unit body, thus opening the gas valve. The lower portion of the tavern unit valve element serves as a probe or pusher that engages the top of the plunger-like valve element in the keg unit; and therefore downward movement of the lever on the tavern unit also effects opening of the valve in the keg unit. With the valves thus opened, pressure gas flows through the connected units and into the top of the keg. Inside the keg is a tube that extends down from the keg unit to near the bottom of the keg, and gas pressure forces beverage up through that tube and the connected keg and tavern units, into the beverage duct.
Heretofore the tavern unit in a system of this type has been so arranged that it was possible to depress the valve actuator lever when the bayonet connection between the units was not fully established and to disengage the bayonet connection with the lever in its lowered, valve-open position. In either case, beverage squirted out of the keg around the loose or incomplete connection between the units, and gas freely escaped through the open gas valve in the tavern unit. In addition to the loss of gas and beverage, this leakage entailed the cost and inconvenience of cleaning up the keg storage cooler and usually involved a change of clothing for the person who had been manipulating the tavern unit.
Such occurrences, although perhaps not frequent, were by no means rare. Perhaps it has not heretofore been obvious that there is a need for an expedient which will prevent such accidents, especially since they always seemed to be preventable with reasonable care and the penalty for carelessness was nothing worse than a mess.
But if the art recognized the desirability of providing some expedient for enforcing coordinated manipulation of the bayonet connection and the valve actuator, the nature of that expedient was by no means obvious. There is no point in preventing an infrequent and relatively minor mishap if the cost of such prevention is substantially greater than the cost of the accident, or if the preventative means introduces a new set of problems. Obviously, control systems technology could suggest various sensing and lockout arrangements that would perform the necessary function but would be impractical. Apparatus associated with keg tapping systems must be capable of surviving very rough handling, must not tend to provide lodgings for dirt, must be capable of being readily cleaned, and--notwithstanding these other requirements--must be dependable and inexpensive.
A most important requirement is that any change in the system should be confined to the tavern unit and should not affect the keg unit. This is because any particular dispensing location requires no more than a few tavern units, whereas the cost of any change in the keg unit must be multiplied by the thousands of kegs in which keg units are installed.
Thus the problem to which the present invention is addressed is one that is fairly simple on its face but is in fact involved with many complications and is made all the more complicated by the need for a solution to it that will be extremely simple.